Mold forming apparatus and method



Feb. 16, 1965 L. JOHNSTON 3,159,284

MOLD FORMING APPARATUS AND msmon Filed May 31, 1962 Fig.l.

lNVENTOR Loyal L. Johnston United States Patent 0 3 169,284 IVESLD FGRMEJG AiPARATUfl AND METHGD Loyal L, .lohnston, Zelienople, Pa, assignor to Eierman Pneumatic Machine Company, Pittsburgh, 2a., a corporaiion of iennsylvania Filed May 31, 1962, Ser. No. 199,979 2 Claims. {i1 22-17) This invention relates to mold forming apparatus and a method of forming a mold and has to do particularly with the formation in an elongated flask of a mold of finely divided mold forming material adapted for the casting of a product in a foundry. Molds made by use of my invention are adapted for the centrifugal casting of elongated hollow articles such as lengths of pipe, for example, cast iron soil pipe and cast steel pressure pipe.

In a number of copending applications including, for example, applications Serial Nos. 118,001 and 118,002, filed lune 19, 1961, the latter of which is now abandoned,

I have disclosed the forming of molds of the general type above referred to by advancing a former through finely divided mold forming material in an elongated flask. I have found that it is important for optimum results that the former have a certain characteristic shape and that the component elements employed in the formation of the mold be relatively proportioned so that the mold forming material is compacted to a predetermined extent. I have also discovered certain other method and apparatus features presently to be described which contribute importantly to the obtaining of optimum results.

For purposes of explanation and illustration I shall describe a mold forming apparatus and method employed in the forming of molds for the centrifugal casting of elongated hollow cylindrical objects. Actually my invention in practical use will be adapted for the formation of molds for the centrifugal casting of lengths of pipe, each pipe length having either a hub at one end and a spigot at the other end or hubs at both ends, but for simplicity the portions of the mold for forming the hub and spigot of single hub pipe or the hubs of double hub pipe are not shown, the mold shown in the drawings being of uniform cross-sectional area throughout its length.

I provide mold forming apparatus comprising an elongated flask adapted to receive finely divided mold forming material, a tapered former and means for advancing the tapered former through the flask with its portion of relatively small transverse cross-sectional area leading to form an elongated cavity in finely divided mold forming material in the flask and compact the mold forming material to form a mold for casting, a portion of the former following the leading portion having relatively great transverse cross-sectional area and also being tapered at such an angle that its surface is more nearly parallel to the axis of the former than the surface of the leading portion so that the leading portion of the former forms the cavity in the mold forming material and tends to somewhat advance the mold forming material in the direction of advance of the former to cause a flow of the mold forming material before it is finally comp-acted to substantially uniformly distribute the mold forming material about the former and the following portion of the former compacts the thus distributed mold forming material. In a preferred form the former has a portion intermediate the leading and following portions of the former, which intermediate portion of the former has a transverse cross-sec- 3,16%,284 Patented Feb. 16, 1965 ice ti-onal area in between the transverse cross-sectional areas of the leading and following portions and which is tapered at an angle in between the angles of taper of the leading and following portions, the intermediate portion of the former consolidating the mold forming material preliminary to the final compacting thereof and insuring optimum distribution of the mold forming material. The former also preferably has a portion of uniform cross-see tional area disposed behind the following portion for smoothing the compacted mold forming material.

My mold forming apparatus preferably includes means for pulling the former through the flask from the end of the flask toward which the former advances. T he pulling means are preferably connected with the forme at the portion thereof of greatest transverse cross-sectional area, i.e., the trailing portion of the former as the former advances through the flask, which avoids uncontrolled lateral motion or fishtailing of the former.

I preferably provide guide means for guiding the former in a predetermined path at the portion of the flask through which the former initially passes until the former has sufficiently compacted the mold forming material so that thereafter the mold being formed in the mold forming material by the former serves to guide the former. Guide means are also prefer-ably provided at the end of the flask toward which the former advances for guiding the pulling means to assist in maintaining the former in a predetermined path as it advance-s through the mold forming material in the flask. Such guide means are preferably mounted to be pushed by the former ahead of it as the former reaches the end of the flask toward which it advances.

The internal cross-sectional area of the flask, the maximum cross-sectional area of the former and the external cross-sectional area of the pulling means are preferably proportioned so that the mold forming material is compacted by the mold forming operation so that its cross-sectional area is reduced at least about 18% and not more than about 50% and preferably at least about 24% and not more than about 35%.

The pulling means may comprise an inner primary pulling element with a secondary element disposed thereabout ahead of the former to produce an optimum effective crosssectional area of the pulling means greater than that of the primary pulling element so that the pulling means occupy a portion of the space within the flask greater than that occupied by the primary pulling element and in consequence limit the capacity of the flask for receiving mold forming material.

As above indicated, the former preferably has a portion of uniform cross-sectional area disposed behind the following portion thereof for smoothing the compacted mold forming material. Such portion of uniform cross-sectional area also serves to guide the former in the mold being formed. in the mold forming material. The pulling means act under tension in cooperation with the portion of the former of uniform cross-sectional area to pull the former through the flask from the end of the flask toward which the former advances whereby the :former is caused to advance in a substantially straight path through the flask as it forms the mold.

I also provide a method of forming in an elongated flask a mold of finely divided mold forming material comprising introducing into the flask relatively uncompacted mold forming material and moving through the 'will presently be made.

mold forming material lengthwise of the flask; preferably b use of ullin means under tension, a former having Y P D its leading portion tapered rearwardly from relatively small to relatively great transverse cross-sectional area and a portion rearwardly of the leading portion which is of uniform cross-sectional area, by the advance of the former through the mold forming material forming an elongated cavity in the 'mold forming material and compacting and smoothing the mold forming material at the periphery of the cavity, starting the former in its path through the flask by guiding it independently of the mold forming material and guiding the former by the mold forming material as it advances therethrough'and compacts and'srnooths the mold forming material; Thus the former is guided by the compacted and smoothed mold forming material. acting against the portion of uniform cross-sectional area of the former as it advances through Other details, objects and advantages of the invention will become apparent as the following description of certain present preferred embodiments thereof and certain present preferred methods of practicing the proceeds.

same

7 Inthe accompanying drawings I have shown certain the formers through the mold forming material in'the FIGURE 6 is a view similar to FIGURE 1 showing the V amazes v Pulling means in the form ofa rod 7 pass freely through the bore 6 and through the hollow portion of the former and have anut applied thereto atthe left-hand end of the former viewing FIGURE 1. The nut 8 bears against the head 8a of the former. The pulling rod '7 .passes toward the right viewing FIGURE 1 from the former 3 axially through the flask 2' and out the righthand end of the flask; 7 At the right-hand end of the flask is a plate 9 fastened to the flask in any suitable manner as by bolts 9:; so as to be in effect integral therewith, the plate 9 having a central opening it in whioh is disposed by a frictional fita guide plug 11 which has a bore 12 of suchdiameter as to guidingly receive the pulling rod '7. l The axis of the bore 12 is coin ident with theaxis of the flask. Any suitable means are provided for pulling the rod 7 toward the right viewing FIGURE 7 1 through the flask 2, the pulling force being applied to the rod-atthe portion thereof projecting out of the righthand end of the'flask.

The flask, former and pulling red are initially assembled in the relative positions shown in FIGURE 1 and finely divided mold forming material such, for example, 'as

" foundry sand '13 is introduced into the flask. The mold forming material may be introduced through either end of the flask before the flask is closed by application of the plates 4 and 9. For example the plate 4 may be permanently. applied to the flask while the. plate 9' may be removable,' and with the former 3 and the pulling rod '7 in the position of FIGURE 1 mold'forming material may he, introduced into the fiask'from the right-hand end,

viewing that figure until the flask is substantially filledwith the mold forming material in relatively uncomipacted form whereupon the plate9 may be applied to close a the flask. Alternatively the plate 9 may he permanently former in its movement through the flask forming, consolidating and compacting the mold forming material to form 'amold, the former being guided in the mold being formed, the former being shown in axial cross section.

Referring now more particularly to the drawings, there is shown in FIGURE 1 a'flask 2 which for simplicity is cylindrical and. of uniform diameter or cross-sectional area from end to end. 'This'form of flask isselected for the purpose of broadly demonstrating the invention since the invention is not dependent upon the employment of a specific form of flask in reference to the end portions thereof. While in actual use in forming molds for the centrifugal casting of cast iro n'soil pipe provision will be made'in the molds either for formation of a hub at one end of the pipe and a spigot at the other end or for the'formation of "hubs at bothends, the provision or non-provision of such portions of the mold is not a limitation upon the presentinventionlso for simplicity I have shown in FIGURE 1 a plain 'cylindrical fiask without any provision for producing a mold having portions for :forming a hub and spigot or hubs at the respective ends of .the pipe to be cast therein.

A former 3 is shown at one end ofthe flask-2 in FIGURE 1. 'The'former 3 maybe of various forms as shown in FIGURES 2,3, 4 and 5 toiwhich reference T he. former of FIGURE 1 is' that :shown in FIGURE 4. The left-hand end of the flask} viewing FIGURE 1 has a plate 4 fastened thereto :in any appropriate manner as by bolts 4a so that'it is. 7 in effect integral with the flask. The plate 4- carries "guide means for the formerin the shape of' a sleeve '5, whose internal diameter is suchthat it has a guiding lit with; the former 3. The sleeve 5 hasits axis coincidingwith'theaxis of the flask and is 'for'the purpose of 5 guiding. the former in a straight-path axially of the flask as'theformer starts tomove through the flask.

' The nose of the fQlIllfiI I'ihfififl bore 6 formed axially therethrough and the former is hollow behind the bore 6.

applied to the flask and the mold forming material may be introduced through the opposite end after which the plate 4 which carries the guide. sleeve .5 may be applied.

Regardless of which end of the fia'sk receives the mold forming'material the former and pulling means will be positioned substantially as shown in FIGURE -1 before the *n'rold forming material is introduced, and after the mold forming material has been introduced the flask will be closed The flask may be oriented in any preferred way.

It may remain at all times with its axis substantially horizontal, in which case the mold forming material will be impelled 'into'the flaskbyany suitable means as well known to those skilled in the art. Alternatively the flask may be uptilted to more or less vertical position with eithtr end upwardly as desired and the mold forming material may be introduced through the upper end of the flask. "Thei-flask may be in any orientation for the mold forming step presently to be described. For 'optimum efliciency I prefer to arrange the flask generall'y ver- "ticallyfor the mold forming step.

Withthe 'flaskfilled with relatively uncompacted mold forming material andwith the elements in the positions shown in'FIGUREl I pull the rod 7 to the right viewing that figure and the former moves through the initially relatively uncompacted mold fdrming material andlforms an elongated axial cavity therein'and consolidatesand compacts the mold forming' material in the flask during its 7 movementtherethrough and' sizes and smooths the surface. of the cavity to form a mold suitable for centrifugal casting." "At the b eginning of the movement of the former through' the flask the former is guided axially of the flask by the sleeveS. As the former advances through the initially relatively uncompacted mold forming ma ter ial 'in the flaskit distributes, consolidates and com pacts'the mold forming material and forms its own guideway in the mold, forming material. Throughout the movement 'of the former'tnrough the flask after the. former movespast the inner endof the guide sleeve 5 the former is guided by the bore of the mold cavity being formed aridjthe rod'7 is guided by the bore- 12 in the guide plug 11. a This is illustrated in FIGURE 6. The

result is that the former moves in a straight line through the flask and forms a straight cavity or bore in the mold forming material while compacting the mold forming material to form the mold. I have found that a straight bore will be formed in the mold forming material even if the flask is warped so that it assumes a somewhat curved shape from end to end. When the nose of the former reaches the guide plug ll. the continued movement of the former toward the right viewing FIGURE 1 dislodges the guide plug 11 from the plate 9 in which the guide plug.

was held by friction which allows the former to move completely through and out of the flask to complete the formation of the mold.

As above indicated, the former shown in FIGURE 1 is of the form shown to enlarged scale in FIGURE 4. The shape of the former and the proportions of the flask, the former and the pulling means are important to optimum mold formation. The former 3 shown in FIG- URE 4 has a nose or leading portion 14 with the bore 6 therethrough having its outer generally conical surface relatively steeply inclined to the axis of the flask, an intermediate portion 15 having its outer generally conical surface somewhat less steeply inclined to the axis of the flask, a following portion 16 having its outer generally conical surface inclined at only a slight angle to the axis of the flask and a rearward portion 17 having an outer generally cylindrical surface whose diameter determines the diameter of the mold being formed. As the former moves through the initially relatively uncompacted mold forming material in the flask the nose or leading portion 14 thereof forms an elongated cavity in the mold forming material and tends to somewhat advance the mold forming material in the direction of advance of the former to cause a flow of themold forming material before it is compacted to substantially uniformly distribute the mold forming material about the former. The portion 14 is inclined to the axis of the flask at a-angle of 12 so that it has a substantial force component acting in the longitudinal direction. This not only tends to somewhat advance the mold forming material in the direction of advance of the former but incident to suchadvance causes the mold forming material in localized parts thereof of relatively low density to shift transversely in'the flask so that the density of the mold forming material as the former moves through it becomes substantially uniform about the former. The intermediate portion 15 of the former is disposed at an angle of 6 to the axis of the flask and hence exerts a substantially smaller axial component of force against the mold forming material and has the primary effect of consolidating the mold forming material preliminary to final compacting thereof and insuring optimum uniform distribution of the mold forming material. The following portion 16 of the former is disposed at an angle of 1 to the axis of the flask and its function is to compact the mold forming material in the flask to its ultimate hardness.

forming material itself constitutes a guide for the former.

The former is started in the right direction by being guided by the sleeve 5 and also of course by the guide plug 11 which guides the pulling rod 7. By the time the portion 17 of the former emerges from the sleeve 5 the mold.

formirn material through which the portion 17 of the former. is passing has been compacted to its ultimate hardness and sized so. that external guidance of the former. (by means such as the sleeve 5) is no longer necessary so long as the pulling rod 7 moves axially of the flask. Thus after the former passes out of the sleeve 5 it is guided by the compacted mold forming material.

The increase in density of the mold forming material The rearward cylindrical portion 17 of the former sizes and smooths the mold ing material which guides the former and which also constitutes the mold cavity is designated C in FIGURE 6.

The shape of the former makes possible the optimum distribution of the mold forming material in the flask transversely of the former and the consolidation and compacting'of the mold forming material to form not only an accurate mold but a guide of the mold forming material itself insuring movement of the former through the flask in a straight line and ultimate formation of astraight mold suitable for centrifugal casting.

The pulling rod 7 is connected with the former at the rearward end of the former although as shown the former is braced against and positioned by the rod at its nose or leading portion. The rod is pulled through the flask so that the rod itself is under tension but the former is under compression since the force imparted to the former is imparted to it at its trailing end. I find that this obviates uncontrolled transverse tilting or other motion of the former commonly referred to as flshtailing and contributes to the formation of a straight accurate uniform mold.

Experiments conducted with the pulling rod connected.

with the former only at the nose portion of the former revealed a tendency of the former to fishtail to some extent. That tendency was overcome by providing for the force pulling the former through the flask to be exerted upon the former at its trailing portion while the pulling means is under tension.

In the former shown in FIGURE 4 which is for the formation of six-inch service weight cast iron soil pipe the diameter of the rearward cylindrical portion 17 of the former is 6% inches, the length of the nose or leading portion 14 is 9 inches, the length of the intermediate portion 15 is 6 inches, the length of the following portion 16 is 2 inches and the length of the rearward cylindrical portion 17 is 4 inches. That former is used in a flask having an internal diameter of 12 inches. The diameter of the pulling rod 7 is 1 inch.

The former shown in FIGURE 2 is for the formation of two inch service weight cast iron soil pipe. This former is designated 3a and has a nose or leading portion 14a, in intermediate portion 15a, a following portion 16a and a rearward cylindrical portion 17a. The portion 14a is inclined to the axis of the flask at an angle of 12, the portion is inclined to the axis of the flask at'an angle of 6 and the portion 16a is inclined to the axis of the flask at an angle of 1. The diameter of the cylindrical portion 17a is 2 inches. The diameter of the pulling rod 7 1 is inch. This former is used in a flask having an internal diameter of 4% inches. The length of the portion 14a of the formerda is 1% inches, the length of the portion 15a is 1 /8 inches, the length of the portion 16a is 2 inches and the length of the portion 17a is 4 inches. The pulling rod 7a passes freely through the forward portion of the former and is threaded into the portion 17a thereof as shown in FIGURE 2.

The former shown in FIGURE 3 is for the formation of four-inch service weight-cast iron soil pipe. This former is designated 3b and has a nose or leading portion 141), an intermediate portion 15b, a following portion 16b and a rearward cylindrical portion 17b. The portion 14b is inclined to the axis of the flask at an angle of 12, the portion 15b is inclined to the axis of the flask atan angle of 6f and the portion 16b is inclined to the axis of the flask at an angle of 1. The diameter of the cylindrical portion 17b is 4%; inches. The diameter of the pulling rod 7 is.

1% inches. This former is used in a flask having an internal diameter of 8'inches. The length of the portion 14b of the former 3b is 5 A3 inches, the length of the portion 15b is 2%; inches, the length of-the portion 16b is 2 inches and the length of the portion 17b is 4 inches. The pulling rod 712 passes freely through the former and is threaded former and is fixed thereto by screws 19;

tion 17cis4 inches;

7 material.

. to. perform its function;

"The-former shown in FIGURES is'iforthe formation 'of' ten-inch service weight cast iron soil pipe. This former is designated 3c and has a nose or leading portion'14c, a following portion 160 and 'a rearward cylindrical portion 17c. T he portion 14; is inclined to the axis of the flask at an angle'of'G and theportion 160 is inclined to the axis of theflask at an angleof 1. The diameter of the cylin drical portion 17c is' 10 /2 .inches.

pulling rod -7,ci 1% inches. This former'is used ina flask having an internal diameter of 14 inchesi f Thelength of "the-portion 1400f the former 3c is 13 inches, the length a of the portion 16c is 3% inches and the length of'the'pon arnut 8c applied thereto aga'inst'the head 8d of the former analogously to the nut 8 of FIGURE 4.

The former of FIGURE difiers from the formers of FIGURES 2, 3 and 4 in thatin FIGURES the rod '70 is in'the-form of a sleeve having an external dia meter of 8% inches is disposed about the rod 7c ahead of the former as shown in FIGURE 5 to produce an optimum efiective cross-sectional area ofthe pulling means greater than that of the primary; pulling element 7c so that'the pulling means considered as theelements 7c and 20 occupy a portion of the space within-the flaskgreater-than that occupied by and the cross-sectional area of the pulling rod. The cross-sectional area of the4 fii' inch diameterformer is 14.18. square 'inches. The cross-sectional area of the Qpulling'rod-is 1.22 square inches. The difference is 12.96

The diameter of the The pulling'rod 70 passes freely through the former as in the form of FIGURE 4 and has square inches;

ing material employed and the condition of the mold forming'material, optimum results in mold formation are obtained when the percentage of" compaction is kept between 24% -'and;35%xand advantages of the invention are obtained when the percentage of compaction is at .least about 18% and not more than about 50%.

While I have shown and described certain present prefered embodiments of the invention and have illustrated certain present preferred methods of practicing the same it is tobe'distinctly understood that the inventhe primary pulling element and a secondary. element 20 the primary pulling element 7:: alone and in consequence limitthe capacity of the flask for receiving mold forming While actually the pulling force is exerted through the rod 7;" the'function of the sleeve 26) is to inso for purposes of'nomenclature the sleeve 20 is referred to as a secondary element'of the pulling means. Itv is den-J tered to the rod 70 by plates 21=and at its rearward end- (itsleft-hand end viewing FIGURES) embraces the'nose of the former. 7 T

V ;In theform of FIGURE '5 nose or leading portionf 1400f the former is inclined at an angle. of 6"to the axis' crease'the'effective cross-sectional area of the pulling rod V also-"being tapered at isuch an angle that its surface is more nearly parallel .to the'axis' of the former than the of the flask instead of at an angle of' 12{as in the case of thenose' or leadingportion of the formers of FIGURES 2, 3 and4. This is found preferable in the formationof gressively increases'as the diameter of the} mold tobe pro duced increasesalthough in FIGURE ;5-,the forward part V 1 the largest diameter molds. Also it willzbe noted thatthe length of the nose or leading portion of the former pro-I of the nose or leading portion 14c of the former is con;

cealed as it is disposed inside the sleeve 20. In the form .of FIGURE 5 since the displacement eflect of/the pulling means is produced the sleeve '20 the diameter of the rod 7c is not important so long asfthe rod is strong enough To form a mold of optimum 'hardness it is important not more than about The preferred range is at the case ofeach mold forming apparatus herein disclosed the compaction is within the preferred range.

The cro ss-se c tional area of the eight-inch internal diameter flask is 50.26 square inches and the cross-sectional area of the 1 /4 inchdiameter rod'7b;is 1.22 square inches so that the cross=sgectional area of theflannular, space between-the flask and the rod is 5026 less 1.22- or 49.04 squareinchesg The reduction in cross-sectional} area of the mold forming material ismeasured by the dilference between the cross-sectional area of the-former least about 24% and not morethan about 35%. In

tion is not limited thereto but'may be otherwise variously embodied and practiced ing claims.

1.'-Mold forming {apparatus comprising an elongated flask adapted to receive finely divided moldvforl ling ma 'tenial, a tapered form-er and means for pulling the taper-ed former through the (flask from the end or". the flask toward which the former adva nces with'the portion of relatively small transverse cross-sectional area of the former; leadingto form an elongated 'cavity in finely divided mold "forming material in the flask-and compact the mold f orrning niaterialhto form a mold for casting, a portion. ofztheiormer following-the leading portion having relatively great transverse cross-sectional area and surface of the,.leading-portion so that the -leading por- 1 tion of the former terms the cavity in the mold form ingmaterial and tends to somewhat advance the mold forming mateIJi althedinectiOn of advance of the former; to. causeaflowfof'the mold forming material before it is finally compact-edto substantial-lyuniformly distribute 'the'rnold forming material about theforrner and the following portion of the former compacts'the thusdis-' tributedmold forming material, the length of the former being but a. fraction offthe lengthof the flask so that during at 'leastlthe major portion of the travel of the former through the flask the 'mold being formed in the H mold forming-material bythe-form'er serves to guide the former, thepulling means extending freely through the leading portion of the former andbeing connected with: theforrner at the'portion thereof of. greatest transverse cross-sectional area.. V

-2. Moldforming apparatus comprising an elongated fiask adapted toreceivefinely divided mold forming'mat erial, a tapered fo'rmenand means for pulling the ta pered :formerfthrougha flask from the endfof the flask toward which the former'adv'ances with the portionof relatively small; transverse cross-sectional area of the I former leading to form an elongated cavity in finely di videdmold fo'rming'materialinthe flask and compact the'mold forming material to form a mold for casting. a portion of thefiormer following the leading portion having relatively greattransverse cross-sectional area and a lso bein g tapered at such? an angle that its surf-ace is v a v To illustrate how the percentage otcompacti'on. is,

computed the form of FIGURE 3 wil1'be'ccnsidered.

moneinearly. paralleltothe axis vof the former than the surface of the leading portion. so that. the leadingportion' or the former forms "the, cavity in the mold formingrnaterial and tends to somewhat, advance th8.m01d

f formingmaterial'in the direction of advance of the former g to cause a flowof the mold forming'material before isfinally compacted to substantially uniformly distribute the mold forming materialnabout the former. and the following portion of the former compacts the thus distributed mold formingmateria'l, the'former'havin g a portion of'uniform cross-sectional area disposed behindthe The percentage of compaction is 12.96 divided by49.04 or 26.4%. While there may be some variation in-the extent of compaction depending upon 'localcond-itions, the typ'e of finely divided mold'formwithinthe scope of the follow 9 10 following portion for smoothing the compacted mold References Cited in the file of this patent forming material, the length of the former being but a fraction of the length of the flask so that during at least UNITED STATES PATENTS the major portion of the travel of the former through 181,368 Smlgh 1876 the flask the mold being formed in the mold forming 5 598,624 w 81 1898 material by the former serves to guide the former through 2019937 Staples 1935 the portion of uniform cross-sectional area thereof, the 2,598,554 Johnston May 27, 1952 pulling means extending freely through the leading por- FO PATENTS tion of the former and being connected with the former g at the portion thereof of greatest transverse cross-sectional 10 

1. MOLD FORMING APPARATUS COMPRISING AN ELONGATED FLASK ADAPTED TO RECEIVE FINELY DIVIDED MOLD FORMING MATERIAL, A TAPERED FORMER AND MEANS FOR PULLING THE TAPERED FORMER THROUGH THE FLASK FROM THE END OF THE FLASK TOWARD WHICH THE FORMER ADVANCES WITH THE PORTION OF RELATIVELY SMALL TRANSVERSE CROSS-SECTIONAL AREA OF THE FORMER LEADING TO FORM AN ELONGATED CAVITY IN FINELY DIVIDED MOLD FORMING MATERIAL IN THE FLASK AND COMPACT THE MOLD FORMING MATERIAL TO FORM A MOLD FOR CASTING, A PORTION OF THE FORMER FOLLOWING THE LEADING PORTION HAVING RELATIVELY GREAT TRANSVERSE CROSS-SECTIONAL AREA AND ALSO BEING TAPERED AT SUCH AN ANGLE THAT ITS SURFACE IS MORE NEARLY PARALLEL TO THE AXIS OF THE FORMER THAN THE SURFACE OF THE LEADING PORTION SO THAT THE LEADING PORTION OF THE FORMER FORMS THE CAVITY IN THE MOLD FORMING MATERIAL AND TENDS TO SONEWHAT ADVANCE THE MOLD FORMING MATERIAL IN THE DIRECTION OF ADVANCE OF THE FORMER TO CAUSE A FLOW OF THE MOLD FORMING MATERIAL BEFORE IT 